Hutchinson-Gilford progeria syndrome (HGPS) is the most dramatic human syndrome of premature aging. Children with this rare condition are normal at birth, but by age 2 they have stopped growing, lost their hair, and shown skin changes and loss of subcutaneous tissue that resemble the ravages of old age. Untreated, they rarely live past adolescence, dying almost always of advanced cardiovascular disease (heart attack and stroke). The classic syndrome has never been observed to recur in families. Our laboratory discovered that nearly all cases of HGPS harbor a de novo point mutation in codon 608 of the LMNA gene. This mutation causes disease by creating an abnormal splice donor, generating an mRNA with an internal deletion of 150 nt. This is translated into a mutant form of the lamin A protein (referred to as progerin) that lacks 50 amino acids near the C-terminus. Normally lamin A is post-translationally processed to add a farnesyl group at the C-terminus, and then the last 18 amino acids are cleaved off to produce mature lamin A. Progerin lacks the recognition site for this final cleavage, and so remains permanently farnesylated. We have shown that this abnormal protein acts as a dominant negative to disrupt the structure of the membrane scaffold. Data from our group has also demonstrated that progerin interferes with proper chromosome segregation during mitosis, and alters the distribution of various histone chromatin marks. A mouse model for HGPS has been developed. Animals carrying a human BAC transgene bearing the codon 608 mutation show progressive loss of smooth muscle cells in the media of large vessels. Thus, the mouse model nicely replicates the cardiovascular phenotype of HGPS. We have tested the use of farnesyl transferase inhibitors (FTIs), to see if these drugs could provide benefit in HGPS by reducing the amount of the toxic progerin protein. Treatment of HGPS fibroblasts growing in cell culture demonstrates that FTIs are capable of reversing the dramatic nuclear blebbing that is the hallmark of the disease. A trial of FTIs in the HGPS mouse model has demonstrated that this drug treatment is capable of preventing and even reversing the cardiovascular phenotype. An open label clinical trial of FTIs in 30 children with the disease was initiated in May 2007, and results have just been published. Homozygotes for the mouse BAC transgenic have also now been bred, and show a considerably more severe phenotype. Those animals are now being used to test the effect of the combination treatment of FTIs, statins, and bisphosphonates. A more recent line of research involves the use of rapamycin to increase turnover of progerin aggregates by activating autophagy. Based on cell culture results, rapamycin shows considerable promise, and we are now initiating a mouse model test of this therapeutic approach. While progerin has a dramatic effect on nuclear structure and mitosis, it also disrupts the connections between the nuclear scaffold and chromatin. The consequences include dysregulation of gene expression and epigenetic modification. To explore this in detail, we are studying passage-matched normal and HGPS fibroblasts, using gene expression microarray analysis and chromatin immunoprecipitation coupled with high throughput sequencing (ChIP-seq) and the Hi-C method that reveals the 3-D structure of chromatin in the interphase nucleus. Of considerable relevance to the study of normal human aging, we have also shown that progerin is made in small amounts in normal individuals, and appears to increase in quantity as cells approach senescence. Recent data points to an interesting connection between shortening of telomeres and activation of alternative splicing of dozens of genes, including production of progerin from a normal LMNA gene. In this way, senescence apparently proceeds by a positive feedback loop, once a cell has reached its maximum life span.

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Project End
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Support Year
10
Fiscal Year
2012
Total Cost
$1,059,860
Indirect Cost
Name
National Human Genome Research Institute
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Collins, Francis S (2016) Seeking a Cure for One of the Rarest Diseases: Progeria. Circulation 134:126-9
Dubose, Amanda J; Lichtenstein, Stephen T; Narisu, Narisu et al. (2013) Use of microarray hybrid capture and next-generation sequencing to identify the anatomy of a transgene. Nucleic Acids Res 41:e70
McCord, Rachel Patton; Nazario-Toole, Ashley; Zhang, Haoyue et al. (2013) Correlated alterations in genome organization, histone methylation, and DNA-lamin A/C interactions in Hutchinson-Gilford progeria syndrome. Genome Res 23:260-9
Gordon, Leslie B; Cao, Kan; Collins, Francis S (2012) Progeria: translational insights from cell biology. J Cell Biol 199:9-13
Conneely, Karen N; Capell, Brian C; Erdos, Michael R et al. (2012) Human longevity and common variations in the LMNA gene: a meta-analysis. Aging Cell 11:475-81
Bradley, Allan; Anastassiadis, Konstantinos; Ayadi, Abdelkader et al. (2012) The mammalian gene function resource: the International Knockout Mouse Consortium. Mamm Genome 23:580-6
Graziotto, John J; Cao, Kan; Collins, Francis S et al. (2012) Rapamycin activates autophagy in Hutchinson-Gilford progeria syndrome: implications for normal aging and age-dependent neurodegenerative disorders. Autophagy 8:147-51
Cao, Kan; Blair, Cecilia D; Faddah, Dina A et al. (2011) Progerin and telomere dysfunction collaborate to trigger cellular senescence in normal human fibroblasts. J Clin Invest 121:2833-44
Verstraeten, Valerie L R M; Peckham, Lana A; Olive, Michelle et al. (2011) Protein farnesylation inhibitors cause donut-shaped cell nuclei attributable to a centrosome separation defect. Proc Natl Acad Sci U S A 108:4997-5002
Cao, Kan; Graziotto, John J; Blair, Cecilia D et al. (2011) Rapamycin reverses cellular phenotypes and enhances mutant protein clearance in Hutchinson-Gilford progeria syndrome cells. Sci Transl Med 3:89ra58

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